Headphone stand with desk clamp

// A headphone stand that clamps to a desk edge, with the hanger arm at the bottom so the
// headphones hang in front of the desk. Built entirely from straight rectangles; corners
// and edges are rounded afterwards as a final polish, never as part of the construction.
// Uses threads.scad by Ryan A. Colyer, released with CC0 into the public domain.
// Published on RemixCAD as remixcad/threads.
use <remixcad/threads/threads.scad>

/* [Parts] */
// Render the assembly, or one part for printing.
part = "both"; // [both, stand, bolt]

/* [Clamp] */
// Thickest desk the clamp opens for.
desk_max = 30; // [10:1:60]
// How far the jaws reach over the desk.
clamp_depth = 40; // [20:1:80]
// Width of the clamp along the desk edge.
clamp_width = 32; // [16:1:60]
// Thickness of the top jaw, resting on the desk.
jaw = 8; // [5:0.5:14]
// Thickness of the bottom jaw, carrying the thread.
foot = 10; // [6:0.5:16]
// Nominal metric size of the clamp bolt, so 8 is an M8.
bolt_size = 8; // [5:1:12]
// How far the bolt can travel up from the bottom jaw.
travel = 18; // [8:1:40]
// Taken off the thread to allow for printing.
tolerance = 0.5; // [0.2:0.05:1]

/* [Hanger] */
// How far the arm reaches out past the desk edge.
arm_length = 60; // [30:1:110]
// Thickness of the arm the headband rests on.
arm_thick = 12; // [8:1:20]
// Height of the lip at the arm end. Zero removes it.
lip = 16; // [0:1:35]
// Thickness of the lip.
lip_thick = 10; // [6:1:16]

/* [Polish] */
// Radius the profile corners are rounded to. Zero keeps them sharp.
round_r = 2.5; // [0:0.5:5]
// Radius the remaining edges are rounded to. Zero keeps them sharp.
edge_r = 1.5; // [0:0.25:3]

/* [Quality] */
// Facets on the rounded polish. More is smoother and slower.
smoothness = 48; // [16:8:96]

/* [Hidden] */
back = 12;
gap = desk_max;
bottom = -(gap + foot);
bolt_x = clamp_depth * 0.55;
bolt_len = foot + travel;
knob_d = 3.2 * bolt_size;
knob_h = 7;

// The polish: a closing pass rounds the concave corners, an opening pass the convex
// ones. Applied over the finished straight shape, never during it.
module polish2d(r) {
  if (r > 0)
    offset(r = r, $fn = smoothness)
      offset(r = -2 * r, $fn = smoothness)
        offset(r = r, $fn = smoothness)
          children();
  else
    children();
}

// ---- Stand ----
// One 2D profile of axis-aligned squares, in the XZ plane.
// Origin: top of the desk at z = 0, the desk edge at x = 0, the desk toward +x.

module profile_raw() {
  // Top jaw, resting on the desk.
  square([clamp_depth, jaw]);
  // Back, spanning the desk edge.
  translate([-back, bottom]) square([back, gap + foot + jaw]);
  // Bottom jaw, carrying the clamp thread.
  translate([0, bottom]) square([clamp_depth, foot]);
  // Arm at the bottom, reaching out past the edge.
  translate([-(back + arm_length), bottom]) square([arm_length, arm_thick]);
  // Lip at the arm end, so the headband cannot slide off.
  if (lip > 0)
    translate([-(back + arm_length), bottom])
      square([lip_thick, arm_thick + lip]);
}

module profile() {
  polish2d(round_r) profile_raw();
}

module stand_body() {
  if (edge_r > 0)
    minkowski() {
      rotate([90, 0, 0])
        linear_extrude(height = clamp_width - 2 * edge_r, center = true)
          offset(r = -edge_r, $fn = smoothness) profile();
      sphere(r = edge_r, $fn = 20);
    }
  else
    rotate([90, 0, 0])
      linear_extrude(height = clamp_width, center = true) profile();
}

module stand() {
  // The clamp thread is cut straight into the bottom jaw.
  ScrewHole(bolt_size, foot + 2, [bolt_x, 0, bottom - 1], [0, 0, 0],
            tolerance = tolerance)
    stand_body();
}

// ---- Clamp bolt ----
// An octagonal knob with grip flats, polished by the same passes; thread above and a
// flat pad at the tip so it does not mark the desk.

module knob2d() {
  polish2d(2) circle(d = knob_d, $fn = 8);
}

module pad2d() {
  polish2d(1.5) circle(d = 1.6 * bolt_size, $fn = 8);
}

module clamp_bolt() {
  if (edge_r > 0)
    translate([0, 0, edge_r])
      minkowski() {
        linear_extrude(height = knob_h - 2 * edge_r)
          offset(r = -edge_r, $fn = smoothness) knob2d();
        sphere(r = edge_r, $fn = 20);
      }
  else
    linear_extrude(height = knob_h) knob2d();
  translate([0, 0, knob_h - 0.01])
    ScrewThread(bolt_size, bolt_len, tolerance = tolerance);
  translate([0, 0, knob_h + bolt_len - 0.01])
    linear_extrude(height = 2.5) pad2d();
}

// ---- Layout ----

if (part == "stand") {
  // On its side, ready to print.
  rotate([90, 0, 0]) translate([0, 0, clamp_width / 2]) stand();
} else if (part == "bolt") {
  clamp_bolt();
} else {
  stand();
  // Assembled: knob under the bottom jaw, thread up through the hole.
  translate([bolt_x, 0, bottom - knob_h - 6]) clamp_bolt();
}